A new method for the synthesis of compound 73/602 has been reported: By cyclocondensantion of 5-methoxyanthranilic acid (I) with 2-pyrrolidinone (II) in the presence of POCl3 or SOCl2.
The compound 73/602 is synthesized by refluxing 5-methoxyanthranilic acid (I) with O-ethyl butyrolactim (II) in dry benzene for 5 hours.